Russia on Monday objected to a move by Ukraine to drag it before the world's oldest arbitration tribunal over access to coastal waters around annexed Crimea.
Moscow's lawyers said the Permanent Court of Arbitration (PCA) in The Hague had no jurisdiction over the case brought by Kiev over the Black Sea, Sea of Azov and Kerch Strait.
Russia snatched the Crimean peninsula from Ukraine in 2014, and Ukraine filed a case with the court in 2016, saying Moscow was illegally blocking access to coastal waters around it.
"This tribunal does not have the jurisdiction to determine Ukraine's claims," Russia's representative Dmitry Lobach told the PCA.
"It is clear that the thrust of Ukraine's claims is over Russia's sovereignty over Crimea and the maritime zones. Despite the high regard with which Russia regards this tribunal, it cannot determine which state is sovereign over Crimea." Lobach added: "In no way can Russia's claim to sovereignty over Crimea be characterised as abusive."